Solid state lights with cooling structures

ABSTRACT

A solid state lighting (SSL) with a solid state emitter (SSE) having thermally conductive projections extending into an air channel, and methods of making and using such SSLs. The thermally conductive projections can be fins, posts, or other structures configured to transfer heat into a fluid medium, such as air. The projections can be electrical contacts between the SSE and a power source. The air channel can be oriented generally vertically such that air in the channel warmed by the SSE flows upward through the channel.

TECHNICAL FIELD

The present technology is related to solid state lighting (SSL) devicesand associated methods of operation and manufacture. In particular, thepresent technology is related to cooling SSL devices with one or moresolid state emitters (SSEs), such as light emitting diodes.

BACKGROUND

SSL devices and SSEs are increasingly in demand for many purposesbecause SSEs efficiently produce high-intensity, high-quality light.Mobile phones, personal digital assistants, digital cameras, MP3players, and other portable devices use SSL devices for backgroundillumination. Applications for SSL devices extend beyond portableelectronic devices and include many types of lights, such as ceilingpanels, desk lamps, refrigerator lights, table lamps, street lights, andautomobile headlights.

There are several types of SSEs, such as semiconductor light-emittingdiodes (LEDs), polymer light-emitting diodes (PLEDs), and organiclight-emitting diodes (OLEDs). Generally, SSEs generate less heat,provide greater resistance to shock and vibration, and have longer lifespans than conventional lighting devices that use filaments, plasma, orgas as sources of illumination (e.g., florescent tubes and incandescentlight bulbs).

A conventional type of SSE is a “white light” LED. White light requiresa mixture of wavelengths to be perceived as such by human eyes. However,LEDs typically only emit light at one particular wavelength (e.g., bluelight), so LEDs must be modified to emulate white light. Oneconventional technique for doing so includes depositing a convertermaterial (e.g., phosphor) on the LED. For example, as shown in FIG. 1A,a conventional SSL device 10 includes a support 2 carrying an LED 4 anda converter material 6 deposited on the LED 4. The LED 4 can include oneor more light emitting components. FIG. 1B is a cross-sectional diagramof a portion of a conventional indium-gallium nitride LED 4. As shown inFIG. 1B, the LED 4 includes a substrate 12, an N-type gallium nitride(GaN) material 14, an indium gallium nitride (InGaN) material 16 (and/orGaN multiple quantum wells), and a P-type GaN material 18 on one anotherin series. Conventional substrates 12 are comprised of sapphire orsilicon. The LED 4 can further include a first contact 20 on the P-typeGaN material 18 and a second contact 22 on the N-type GaN material 14.Referring to both FIGS. 1A and 1B, in operation, the InGaN material 16of the LED 4 emits a blue light that stimulates the converter material 6to emit a light (e.g., a yellow light) at a desired frequency. Thecombination of the blue and yellow emissions appears white to human eyesif matched appropriately.

Another conventional construction of an SSL device 21 is shown in FIG.2. The SSL device 21 has a support 23 upon which a plurality of LEDs 24are mounted. The device 21 also includes a converter material 26, and alens 28 formed over the LEDs 24. The converter material 26 can be formeddirectly on the lens 28 as shown in FIG. 2, or the converter material 26can be formed elsewhere such that light from the LEDs 24 passes throughthe converter material 26.

Although LEDs produce less heat than conventional lighting devices, LEDscan produce enough heat to increase the rate at which some of the heatsensitive semiconductor and optical components deteriorate. Theconverter material 6, for example, deteriorates relatively rapidly athigher temperatures such that over time the converter material 6 emitslight at a different frequency than the desired frequency. The combinedemissions accordingly appear off-white and may reduce the color fidelityof electronic devices. The junctions between semiconductor materialsthat produce the light also deteriorate at higher temperatures.Therefore, it would be desirable to improve the cooling in SSEs and/orSSL devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a partially schematic cross-sectional view of an SSL devicein accordance with the prior art.

FIG. 1B is a partially schematic cross-sectional view of an LED inaccordance with the prior art.

FIG. 2 is a partially schematic cross-sectional view of an SSL device inaccordance with the prior art.

FIG. 3A is a partially schematic cross-sectional view of an SSL devicein accordance with an embodiment of the present technology.

FIG. 3B is a partially schematic side view of an SSE having thermallyconductive projections in accordance with embodiments of the presenttechnology.

FIG. 3C is a partially schematic back view of an SSE having thermallyconductive projections in accordance with embodiments of the presenttechnology.

FIG. 3D is a partially schematic side view of an SSE having thermallyconductive projections and electrical contacts in accordance withembodiments of the present technology.

FIG. 4A is a partially schematic bottom plan view of a rectangular SSLdevice in accordance with an embodiment of the present technology.

FIG. 4B is a partially schematic bottom plan view of a circular SSLdevice in accordance with another embodiment of the present technology.

FIG. 5 is a partially schematic view of an SSL device having an airpressurizer and shroud in accordance with an embodiment of the presenttechnology.

FIG. 6 is a partially schematic side view of an SSL device in accordancewith an embodiment of the present technology.

FIG. 7 is a partially schematic cross-sectional view of an SSL device inaccordance with an embodiment of the present technology.

DETAILED DESCRIPTION

Various embodiments of solid state lights (“SSLs”) and associatedmethods of manufacturing SSLs are described below. The term “SSL”generally refers to “solid state light” and/or “solid state lighting”according to the context in which it is used. The terms “SSL emitter” or“solid state emitter” (“SSE”) generally refer to solid state componentsthat convert electrical energy into electromagnetic radiation in thevisible, ultraviolet, infrared and/or other spectra. SSEs includelight-emitting diodes (LEDs), which are semiconductor diodes thatconvert electrical energy into electromagnetic radiation in a desiredspectrum. SSEs can also include polymer light-emitting diodes (PLEDs)and organic light-emitting diodes (OLEDs). The term “phosphor” generallyrefers to a material that can continue emitting light after exposure toenergy (e.g., electrons and/or photons). A person skilled in therelevant art will understand that the new technology may have additionalembodiments and that the new technology may be practiced without severalof the details of the embodiments described below with reference toFIGS. 3A-7.

FIG. 3A is a partially schematic side cross-sectional view of an SSLdevice 100 according to several embodiments of the present technology.The SSL device 100 can include a housing 110 having a front 112, a back114, a side section 116 between the front 112 and the back 114, and abase 118 at the back 114. The side section 116 can include an inner wall117 a, an outer wall 117 b, and a channel 120 passing through the sidesection 116 between the inner and outer walls 117 a, 117 b. The channel120 can have an inlet 122 at the front 112 of the housing 110 and anoutlet 124 at the back 114 of the housing 110. The housing 110 can alsoinclude a chamber 130 defined by the inner wall 117 a of the sidesection 116 and the base 118. The SSL device 100 can further include areflector 119 mounted to the base 118 in the chamber 130, and aplurality of SSEs 140 mounted to the side section 116 to face thereflector 119. As described in more detail below, the SSEs 140 can havean active portion 142 that emits light toward the reflector 119 and aback portion 144 mounted to the side section 116. The reflector 119directs the light from the SSEs 140 along a primary output direction160, and the SSL device 100 can also include a lens 162 over the chamber130 in the optical path of the primary output direction 160.

In several embodiments the SSEs 140 can be positioned and angledrelative to the reflector 119 such that the reflector 119 directssubstantially all of the light out of the SSL device 100. For example,the SSEs 140 can emit light directed principally in one direction normalto the surface of the active portions 142 of the SSEs 140. It isgenerally advantageous to output as much light as possible from the SSLdevice 100 and still have a compact design. As such, the SSEs 140 can bepositioned relative to the reflector 119 such that the reflector 119directs light from a first edge 140 a of the SSEs 140 past a second edge140 b of the SSEs 140. Additionally, the SSEs 140 and reflector can beconfigured such that light from the second edge 140 b of the SSEs 140 isdirected at an apex 132 of the reflector 119 to prevent light from thesecond edge 140 b of the SSEs 140 from missing the reflector 119 andstriking an opposing SSE 140 (or other component). This arrangementoutputs more light from the SSL device 100 and avoids accumulatingadditional heat in the SSL device 100 that would otherwise occur iflight were reflected back into the SSL device 100. In some embodiments,the reflector 119 can be angled relative to the primary direction 160 bya first angle (Φ). The front 142 of the SSEs 140 can be angled relativeto the primary direction 160 by a second angle (θ) and the reflector 119and the front 142 can be angled relative to one another by a third angle(α). The first angle (Φ) can be approximately equal to the second angle(θ) plus the third angle (α).

In several embodiments, at least a portion of the SSEs 140 is exposed tothe channel 120 in the side section 116. For example, the back 144 ofthe SSEs 140 can be exposed in the channel 120. The channel 120 can beoriented at a sufficiently high angle relative to horizontal such thatair in the channel 120 heated by the SSEs 140 rises and draws cool airinto the lower portion of the channel to produce a passive, naturalcooling flow of air across a surface of the SSEs 140. In severalembodiments, the SSEs 140 can be mounted generally parallel with thechannel 120. In other embodiments, the SSEs 140 are not necessarilyparallel with the channel 120, but can be mounted at a sufficient anglerelative to horizontal such that heated air in the channel 120 rises andcauses the cooling air flow through the channel 120.

In several embodiments, at least one of the inlet 122 and the outlet 124is open to ambient air that is sufficiently cooler than the SSEs 140 tomaintain the temperature of the SSEs 140 within a desired operatingrange. In some applications, an air pressurizer 150, such as a fan,(shown conceptually in FIGS. 3A and 5) can be positioned near the inlet122, the outlet 124, or at both the inlet 122 and the outlet 124 toactively drive the cooling air through the channel 120. The airpressurizer 150 can also be within the channel 120. Depending on theposition of the air pressurizer 150 relative to the inlet 122 and outlet124, the air pressurizer can create positive pressure to “push” air intothe inlet 122, or negative pressure to “pull” air from the outlet 124.If the air pressurizer 150 is within the channel 120, of course, the airpressurizer can create positive pressure between the air pressurizer 150and the outlet 124, and negative pressure between the air pressurizer150 and the inlet 122. The channel 120 can have a first width near theinlet 122 and a second width near the outlet 124 to create advantageousair pressure in the channel 120. For example, the first width can besmaller than the second width to create a Joule-Thomson expansion zone125 in the channel 120 to further draw air into the channel 120.

The back portion 144 of the SSEs 140 can include a heat sink made of athermally and/or electrically conductive material, such as copper (Cu),aluminum (Al), or a highly thermally conductive alloy. In severalembodiments, the back portion 144 can include projections 146, such asfins, posts, or other features that increase the thermally conductivesurface area of the back portion 144. FIGS. 3B-D illustrate severalconfigurations of the projections 146 according to embodiments of thepresent technology. FIG. 3B shows a cross-sectional view of anembodiment of a back portion 144 having a shallow section 147 coveringthe backside of the active portion 142 and several elongated, generallyrectilinear projections 146 a extending from the shallow section 147.Alternatively, back portion 144 does not need to have the shallowsection 147 such that the individual projections 146 a can be separatedfrom one another with the backside of the active portion 142 exposedbetween the projections 146 a. The projections 146 a can define conduits148 parallel to the airflow through the channel 120 (FIG. 3A), or theycan be angled or otherwise non-parallel with the airflow in the channel120 according to known heat transfer techniques.

FIG. 3C is a view of another embodiment of the back portion 144 of theSSE 140 that includes projections 146 b comprising a plurality of postsextending from the backside of the active portion 142 of the SSE 140.The projections 146 b can be arranged in rows and columns, or they canbe staggered in other arrangements. As with other embodiments, theprojections 146 b can project from a shallow section integral with theprojections 146 b.

Other suitable heat-exchanging structures can be associated with the SSE140. For example, FIG. 3D illustrates another embodiment of the presenttechnology in which the back portion 144 includes projections 146 c and146 d made from an electrically conductive material. The active portion142 of the SSE 140 can include electrical contacts 151 a and 151 b(e.g., n and p contacts) that are electrically coupled to the projectionportions 146 c and 146 d, respectively. In other embodiments, theprojections 146 c and 146 d can be made from a dielectric material andinclude interconnects electrically connected to the electrical contacts151 a, 151 b.

FIGS. 4A and 4B are bottoms plan views of specific embodiments of SSLdevices 400 a and 400 b, respectively. More specifically, the SSL device400 a in FIG. 4A is generally rectilinear, and the SSL device 400 bshown in FIG. 4B can be either hexagonal or circular. Like referencenumbers generally refer to similar or even identical components in FIGS.3A, 4A and 4B.

Referring to FIG. 4A, the SSL device 400 a includes an elongatedreflector 119 a composed of two generally flat, rectangular reflectivesurfaces 210. In this embodiment, the SSL device 400 a has separate sidesections 116, and each side section 116 has a plurality of channels 120.The SSEs 140 can be arranged in rows 170 flanking each surface 210 ofthe reflector 119 a such that the active portions 142 face thereflective surfaces 210 and the back portion 144 are in or otherwiseexposed to the channels 120. The SSL device 400 a can include anysuitable number of SSEs 140 arranged in the rows 170. As explainedabove, the SSEs 140 heat the air in the channels 120, which in turndraws cooler ambient air into the channels 120 and across the backportions 144 to cool the SSEs 140.

Referring to FIG. 4B, the SSL device 400 b has a rounded or circularhousing 410 and a reflector 119 b. The reflector 119 b can be conical orfaceted (e.g., pyramidal). The reflector 119 b of the SSL device 400 bshown in FIG. 4B, for example, is faceted and includes six facets 419configured to reflect the light from six corresponding SSEs 140. Inother embodiments, however, the SSL device 400 b can include anysuitable number of facets and SSEs 140. The reflector 119 b can also bea truncated faceted structure with a flat top surface 420 defining theapex.

The SSL device 400 b can also have a planar support 411 that has bevelededges 412. The angle of the beveled edges 412 can vary according to thenumber of sides. For example, a configuration with six sides has bevelsof 60°. The beveled edges 412 of neighboring supports 411 can abut oneanother around the SSL device 400. The SSL device 400 b can also haveone or more SSEs 140 mounted to the planar supports 411. In oneembodiment, the SSEs 140 can be mounted to the planar supports 411 usingconventional planar mounting techniques and equipment while the supports411 are flat and before the supports 411 are joined to the SSL device400 b. As with other embodiments shown and described above, the SSLdevice 400 b can include one or more channels 120 through which coolingair can be drawn to cool the SSEs 140.

FIG. 5 illustrates an SSL device 500 according to further embodiments ofthe present technology that incorporates the SSL device 100 shown inFIG. 3A with an air pressurizer 150 within a shroud 510. The airpressurizer 150 can include a fan (as shown in FIG. 5) or any otherpressurizing mechanism. In this embodiment, the air pressurizer 150 ispositioned near the back 114 of the SSL device 500 and the shroud 510covers the outlets 124 of the channel 120. The shroud 510 can includeexhaust ports 520 through which the heated air is ejected from the SSLdevice 500. In other embodiments, other mechanisms for pressurizing theair can be used in place of (or in addition to) the air pressurizer 150.In some embodiments, the air pressurizer 150 can be placed at anotherlocation relative to the channels 120 and the SSEs 140. For example, asmall fan (or a series of fans) can be positioned in the channels 120 ornear the inlet 122 to force air through the channels 120 with positivepressure rather than pulling air with negative pressure. Otherembodiments of the SSL device 500 can use the SSL devices 400 a (FIG.4A) and/or 400 b (FIG. 4B) with the air pressurizer 150 and shroud 510instead of the SSL device 100 (FIG. 3A).

FIG. 6 shows yet another SSL device 600 according to several embodimentsof the present technology in which the active portions 142 of the SSEs140 are mounted directly to the outer portion of a side section 616. Theside section 616 along with the base 118 define a chamber 630. The sidesection 616 can include electrical contacts 151 a and 151 b electricallycoupled to corresponding contacts of the SSEs 140, and the side section616 can be sufficiently thermally conductive to operate as a heat sinkfor the SSEs 140. The SSL device 600 can further include a channel 620that has an inlet 622 and an outlet 624. A portion of the channel 620 isa “virtual channel” (shown in dotted lines) that extends through thechamber 630 along the inner surface of the side section 616 and over theactive portions 142 of the SSEs 140. Similar to other embodimentsdescribed above, the heated air in the chamber 630 rises and creates apassive, cooling air flow F that flows over the active portions 142 ofthe SSEs 140.

FIG. 7 illustrates an SSL device 700 in accordance with still furtherembodiments of the present technology. The SSL device 700 can include anSSE 140 with an active portion 142 and a thermally conductive backportion 144 with projections, such as fins or posts. The SSE 140 canhave a lens 762 aligned with the active portion 142. The SSE 140 can bemounted to a support 710 including a channel 720 passing across theprojections. The SSL device 700 can be situated to emit light in agenerally horizontal direction 160 with the support 710 extendinggenerally vertically such as on a wall, in a computer monitor ortelevision set, or in another generally vertical structure. The channel720 can be open to an ambient source of air at an inlet and/or outlet(not shown) of the channel 720. In some embodiments, the channel 720 caninclude an expansion zone 125 above the projections or a fan (not shown,similar to other embodiments) to further induce air flow across theprojections. The projections can be electrically connected to the SSE140 and to an external contact in the support 710.

The lenses 162 and 762 of the embodiments described above in FIGS. 3A-7can be formed of injection molded silicone or other suitable material.The lenses 162 and 762 can include a converter material such asphosphor. When light from the SSEs 140 passes through the convertermaterial, the converter material emits light of a desired color andquality. The converter material can be placed anywhere in an opticalpath of the SSEs 140, including on or in the lens 162 or another cover,or separate from a lens or cover. Alternatively, the converter materialcan be placed in a phosphor well. For example, in one embodiment, theconverter material can include a phosphor containing cerium(III)-dopedyttrium aluminum garnet (YAG) at a particular concentration for emittinga range of colors from green to yellow to red under photoluminescence.In other embodiments, the converter material can include neodymium-dopedYAG, neodymium-chromium double-doped YAG, erbium-doped YAG,ytterbium-doped YAG, neodymium-cerium double-doped YAG,holmium-chromium-thulium triple-doped YAG, thulium-doped YAG,chromium(IV)-doped YAG, dysprosium-doped YAG, samarium-doped YAG,terbium-doped YAG, and/or other suitable phosphor compositions. Thelenses 162 and 762 can simply transmit the light from the SSEs 140 andconverter material or it can further focus or otherwise altercharacteristics of the light.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but well-known structures and functions have not been shown or describedin detail to avoid unnecessarily obscuring the description of theembodiments of the invention. Where the context permits, singular orplural terms may also include the plural or singular term, respectively.Unless the word “or” is associated with an express clause indicatingthat the word should be limited to mean only a single item exclusivefrom the other items in reference to a list of two or more items, thenthe use of “or” in such a list shall be interpreted as including (a) anysingle item in the list, (b) all of the items in the list, or (c) anycombination of the items in the list.

Also, it will be appreciated that specific embodiments described aboveare for purposes of illustration and that various modifications may bemade without deviating from the invention. Aspects of the technologydescribed in the context of particular embodiments may be combined oreliminated in other embodiments. For example, the fan and motor can bereplaced with other air-pressurizing mechanisms. Further, whileadvantages (e.g., heat dissipation mechanisms) associated with certainembodiments of the technology may have been described in the context ofthose embodiments, other embodiments may also exhibit such advantages,and not all embodiments need necessarily exhibit such advantages to fallwithin the scope of the technology. Accordingly, the present technologyand associated technology can encompass other embodiments not expresslyshown or described herein.

I claim:
 1. A solid state lighting device (SSL), comprising: a housinghaving a front, a back, a chamber from which light projects toward thefront along a primary light direction, a side section outward of thechamber, and a channel along a portion of the side section and outwardof the chamber, wherein at least a portion of the channel is inclined atan angle relative to horizontal and has an inlet, and an outlet abovethe inlet; and a solid state emitter (SSE) carried by the housing at theside section, the SSE having an active portion and a back portion, theactive portion facing inwardly toward the chamber at an acute anglerelative to the primary light direction, and one of the active portionand the back portion being exposed to the channel; wherein the channelhas an inlet and an outlet that are configured to provide an airflowthrough the chamber that passes over the active portion of the SSE.
 2. Asolid state lighting device (SSL), comprising: a housing having a front,a back, a chamber, a side section between the front and the back, and achannel outward of the chamber and passing along the side section fromthe front to the back, wherein light exits the chamber along a primarylight direction of the SSL device; and a solid state emitter (SSE)having a light-emitting active portion facing inwardly toward thechamber at an angle with respect to the primary light direction suchthat the SSE emits light toward the back of the housing and a backportion facing toward the side section, the SSE being carried by thehousing at a sufficient angle relative to horizontal such that air inthe channel is heated by the SSE, rises, and draws air into a lowerportion of the channel at the front of the housing to produce a coolingflow of air across at least one of the active portion side or the backportion of the SSE.
 3. The SSL device of claim 2 wherein the backportion of the SSE includes a plurality of thermally conductiveprojections extending into the channel.
 4. The SSL device of claim 2wherein the channel is open to ambient air at one of the front or theback of the housing.
 5. The SSL device of claim 2, further comprising anair pressurizer positioned relative to the channel to drive air throughthe channel.
 6. The SSL device of claim 2, further comprising areflector in an optical path of the SSE, wherein light from the SSE isreflected from the reflector and out of the SSL device.
 7. The SSLdevice of claim 2, wherein: the housing has a side section including anouter wall and an inner wall that together define the channel; thechannel has an expansion zone above the SSE; and the back portion of theSSE is exposed to the channel.
 8. A solid state lighting (SSL) device,comprising: a housing having a front, a back and side section defining achamber, wherein light exits the chamber along a primary light directionof the SSL device; a plurality of solid state emitters (SSEs) at theside section and having an active portion facing inwardly toward thechamber and away from the front; a channel in the housing passing alongthe side section from the front of the housing to the back of thehousing, the channel being positioned outwardly of the chamber, whereina portion of individual SSEs is exposed to the channel, and wherein thechannel is oriented such that air in the channel heated by the SSEsflows through the channel.
 9. The SSL device of claim 8, furthercomprising a reflector in the chamber, wherein the SSEs face thereflector such that light from the SSEs is reflected from the reflectorout of the SSL device.
 10. The SSL device of claim 9 wherein thereflector comprises a first surface and a second surface, and whereinthe SSEs are arranged in a first row and a second row with the first rowof SSEs directed toward the first surface and the second row of SSEsdirected toward the second surface.
 11. The SSL device of claim 9wherein the reflector comprises a cone, and wherein the SSEs arearranged in a generally circular pattern facing the cone.
 12. The SSLdevice of claim 9 wherein the reflector comprises discrete facets, andwherein individual SSE face a corresponding one of the discrete facets.13. The SSL device of claim 8 wherein the channel is oriented generallyvertically.
 14. The SSL device of claim 8 wherein: the SSL device has aprimary lighting direction; a surface of the reflective base is angledrelative to the primary lighting direction by a first angle, phi; alighting surface of the SSE is angled relative to the primary lightingdirection by a second angle, theta; the surface of the reflective baseand the lighting surface are angled relative to one another by a thirdangle, alpha; and the first angle, phi, is approximately equal to thethird angle, alpha, plus the second angle, theta.